Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * astreamer_tar.c
4 : *
5 : * This module implements three types of tar processing. A tar parser
6 : * expects unlabelled chunks of data (e.g. ASTREAMER_UNKNOWN) and splits
7 : * it into labelled chunks (any other value of astreamer_archive_context).
8 : * A tar archiver does the reverse: it takes a bunch of labelled chunks
9 : * and produces a tarfile, optionally replacing member headers and trailers
10 : * so that upstream astreamer objects can perform surgery on the tarfile
11 : * contents without knowing the details of the tar format. A tar terminator
12 : * just adds two blocks of NUL bytes to the end of the file, since older
13 : * server versions produce files with this terminator omitted.
14 : *
15 : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
16 : *
17 : * IDENTIFICATION
18 : * src/fe_utils/astreamer_tar.c
19 : *-------------------------------------------------------------------------
20 : */
21 :
22 : #include "postgres_fe.h"
23 :
24 : #include <time.h>
25 :
26 : #include "common/logging.h"
27 : #include "fe_utils/astreamer.h"
28 : #include "pgtar.h"
29 :
30 : typedef struct astreamer_tar_parser
31 : {
32 : astreamer base;
33 : astreamer_archive_context next_context;
34 : astreamer_member member;
35 : size_t file_bytes_sent;
36 : size_t pad_bytes_expected;
37 : } astreamer_tar_parser;
38 :
39 : typedef struct astreamer_tar_archiver
40 : {
41 : astreamer base;
42 : bool rearchive_member;
43 : } astreamer_tar_archiver;
44 :
45 : static void astreamer_tar_parser_content(astreamer *streamer,
46 : astreamer_member *member,
47 : const char *data, int len,
48 : astreamer_archive_context context);
49 : static void astreamer_tar_parser_finalize(astreamer *streamer);
50 : static void astreamer_tar_parser_free(astreamer *streamer);
51 : static bool astreamer_tar_header(astreamer_tar_parser *mystreamer);
52 :
53 : static const astreamer_ops astreamer_tar_parser_ops = {
54 : .content = astreamer_tar_parser_content,
55 : .finalize = astreamer_tar_parser_finalize,
56 : .free = astreamer_tar_parser_free
57 : };
58 :
59 : static void astreamer_tar_archiver_content(astreamer *streamer,
60 : astreamer_member *member,
61 : const char *data, int len,
62 : astreamer_archive_context context);
63 : static void astreamer_tar_archiver_finalize(astreamer *streamer);
64 : static void astreamer_tar_archiver_free(astreamer *streamer);
65 :
66 : static const astreamer_ops astreamer_tar_archiver_ops = {
67 : .content = astreamer_tar_archiver_content,
68 : .finalize = astreamer_tar_archiver_finalize,
69 : .free = astreamer_tar_archiver_free
70 : };
71 :
72 : static void astreamer_tar_terminator_content(astreamer *streamer,
73 : astreamer_member *member,
74 : const char *data, int len,
75 : astreamer_archive_context context);
76 : static void astreamer_tar_terminator_finalize(astreamer *streamer);
77 : static void astreamer_tar_terminator_free(astreamer *streamer);
78 :
79 : static const astreamer_ops astreamer_tar_terminator_ops = {
80 : .content = astreamer_tar_terminator_content,
81 : .finalize = astreamer_tar_terminator_finalize,
82 : .free = astreamer_tar_terminator_free
83 : };
84 :
85 : /*
86 : * Create a astreamer that can parse a stream of content as tar data.
87 : *
88 : * The input should be a series of ASTREAMER_UNKNOWN chunks; the astreamer
89 : * specified by 'next' will receive a series of typed chunks, as per the
90 : * conventions described in astreamer.h.
91 : */
92 : astreamer *
93 0 : astreamer_tar_parser_new(astreamer *next)
94 : {
95 0 : astreamer_tar_parser *streamer;
96 :
97 0 : streamer = palloc0_object(astreamer_tar_parser);
98 0 : *((const astreamer_ops **) &streamer->base.bbs_ops) =
99 : &astreamer_tar_parser_ops;
100 0 : streamer->base.bbs_next = next;
101 0 : initStringInfo(&streamer->base.bbs_buffer);
102 0 : streamer->next_context = ASTREAMER_MEMBER_HEADER;
103 :
104 0 : return &streamer->base;
105 0 : }
106 :
107 : /*
108 : * Parse unknown content as tar data.
109 : */
110 : static void
111 0 : astreamer_tar_parser_content(astreamer *streamer, astreamer_member *member,
112 : const char *data, int len,
113 : astreamer_archive_context context)
114 : {
115 0 : astreamer_tar_parser *mystreamer = (astreamer_tar_parser *) streamer;
116 0 : size_t nbytes;
117 :
118 : /* Expect unparsed input. */
119 0 : Assert(member == NULL);
120 0 : Assert(context == ASTREAMER_UNKNOWN);
121 :
122 0 : while (len > 0)
123 : {
124 0 : switch (mystreamer->next_context)
125 : {
126 : case ASTREAMER_MEMBER_HEADER:
127 :
128 : /*
129 : * If we're expecting an archive member header, accumulate a
130 : * full block of data before doing anything further.
131 : */
132 0 : if (!astreamer_buffer_until(streamer, &data, &len,
133 : TAR_BLOCK_SIZE))
134 0 : return;
135 :
136 : /*
137 : * Now we can process the header and get ready to process the
138 : * file contents; however, we might find out that what we
139 : * thought was the next file header is actually the start of
140 : * the archive trailer. Switch modes accordingly.
141 : */
142 0 : if (astreamer_tar_header(mystreamer))
143 : {
144 0 : if (mystreamer->member.size == 0)
145 : {
146 : /* No content; trailer is zero-length. */
147 0 : astreamer_content(mystreamer->base.bbs_next,
148 0 : &mystreamer->member,
149 : NULL, 0,
150 : ASTREAMER_MEMBER_TRAILER);
151 :
152 : /* Expect next header. */
153 0 : mystreamer->next_context = ASTREAMER_MEMBER_HEADER;
154 0 : }
155 : else
156 : {
157 : /* Expect contents. */
158 0 : mystreamer->next_context = ASTREAMER_MEMBER_CONTENTS;
159 : }
160 0 : mystreamer->base.bbs_buffer.len = 0;
161 0 : mystreamer->file_bytes_sent = 0;
162 0 : }
163 : else
164 0 : mystreamer->next_context = ASTREAMER_ARCHIVE_TRAILER;
165 0 : break;
166 :
167 : case ASTREAMER_MEMBER_CONTENTS:
168 :
169 : /*
170 : * Send as much content as we have, but not more than the
171 : * remaining file length.
172 : */
173 0 : Assert(mystreamer->file_bytes_sent < mystreamer->member.size);
174 0 : nbytes = mystreamer->member.size - mystreamer->file_bytes_sent;
175 0 : nbytes = Min(nbytes, len);
176 0 : Assert(nbytes > 0);
177 0 : astreamer_content(mystreamer->base.bbs_next,
178 0 : &mystreamer->member,
179 0 : data, nbytes,
180 : ASTREAMER_MEMBER_CONTENTS);
181 0 : mystreamer->file_bytes_sent += nbytes;
182 0 : data += nbytes;
183 0 : len -= nbytes;
184 :
185 : /*
186 : * If we've not yet sent the whole file, then there's more
187 : * content to come; otherwise, it's time to expect the file
188 : * trailer.
189 : */
190 0 : Assert(mystreamer->file_bytes_sent <= mystreamer->member.size);
191 0 : if (mystreamer->file_bytes_sent == mystreamer->member.size)
192 : {
193 0 : if (mystreamer->pad_bytes_expected == 0)
194 : {
195 : /* Trailer is zero-length. */
196 0 : astreamer_content(mystreamer->base.bbs_next,
197 0 : &mystreamer->member,
198 : NULL, 0,
199 : ASTREAMER_MEMBER_TRAILER);
200 :
201 : /* Expect next header. */
202 0 : mystreamer->next_context = ASTREAMER_MEMBER_HEADER;
203 0 : }
204 : else
205 : {
206 : /* Trailer is not zero-length. */
207 0 : mystreamer->next_context = ASTREAMER_MEMBER_TRAILER;
208 : }
209 0 : mystreamer->base.bbs_buffer.len = 0;
210 0 : }
211 0 : break;
212 :
213 : case ASTREAMER_MEMBER_TRAILER:
214 :
215 : /*
216 : * If we're expecting an archive member trailer, accumulate
217 : * the expected number of padding bytes before sending
218 : * anything onward.
219 : */
220 0 : if (!astreamer_buffer_until(streamer, &data, &len,
221 0 : mystreamer->pad_bytes_expected))
222 0 : return;
223 :
224 : /* OK, now we can send it. */
225 0 : astreamer_content(mystreamer->base.bbs_next,
226 0 : &mystreamer->member,
227 0 : data, mystreamer->pad_bytes_expected,
228 : ASTREAMER_MEMBER_TRAILER);
229 :
230 : /* Expect next file header. */
231 0 : mystreamer->next_context = ASTREAMER_MEMBER_HEADER;
232 0 : mystreamer->base.bbs_buffer.len = 0;
233 0 : break;
234 :
235 : case ASTREAMER_ARCHIVE_TRAILER:
236 :
237 : /*
238 : * We've seen an end-of-archive indicator, so anything more is
239 : * buffered and sent as part of the archive trailer. But we
240 : * don't expect more than 2 blocks.
241 : */
242 0 : astreamer_buffer_bytes(streamer, &data, &len, len);
243 0 : if (len > 2 * TAR_BLOCK_SIZE)
244 0 : pg_fatal("tar file trailer exceeds 2 blocks");
245 0 : return;
246 :
247 : default:
248 : /* Shouldn't happen. */
249 0 : pg_fatal("unexpected state while parsing tar archive");
250 0 : }
251 : }
252 0 : }
253 :
254 : /*
255 : * Parse a file header within a tar stream.
256 : *
257 : * The return value is true if we found a file header and passed it on to the
258 : * next astreamer; it is false if we have reached the archive trailer.
259 : */
260 : static bool
261 0 : astreamer_tar_header(astreamer_tar_parser *mystreamer)
262 : {
263 0 : bool has_nonzero_byte = false;
264 0 : int i;
265 0 : astreamer_member *member = &mystreamer->member;
266 0 : char *buffer = mystreamer->base.bbs_buffer.data;
267 :
268 0 : Assert(mystreamer->base.bbs_buffer.len == TAR_BLOCK_SIZE);
269 :
270 : /* Check whether we've got a block of all zero bytes. */
271 0 : for (i = 0; i < TAR_BLOCK_SIZE; ++i)
272 : {
273 0 : if (buffer[i] != '\0')
274 : {
275 0 : has_nonzero_byte = true;
276 0 : break;
277 : }
278 0 : }
279 :
280 : /*
281 : * If the entire block was zeros, this is the end of the archive, not the
282 : * start of the next file.
283 : */
284 0 : if (!has_nonzero_byte)
285 0 : return false;
286 :
287 : /*
288 : * Parse key fields out of the header.
289 : */
290 0 : strlcpy(member->pathname, &buffer[TAR_OFFSET_NAME], MAXPGPATH);
291 0 : if (member->pathname[0] == '\0')
292 0 : pg_fatal("tar member has empty name");
293 0 : member->size = read_tar_number(&buffer[TAR_OFFSET_SIZE], 12);
294 0 : member->mode = read_tar_number(&buffer[TAR_OFFSET_MODE], 8);
295 0 : member->uid = read_tar_number(&buffer[TAR_OFFSET_UID], 8);
296 0 : member->gid = read_tar_number(&buffer[TAR_OFFSET_GID], 8);
297 0 : member->is_directory =
298 0 : (buffer[TAR_OFFSET_TYPEFLAG] == TAR_FILETYPE_DIRECTORY);
299 0 : member->is_link =
300 0 : (buffer[TAR_OFFSET_TYPEFLAG] == TAR_FILETYPE_SYMLINK);
301 0 : if (member->is_link)
302 0 : strlcpy(member->linktarget, &buffer[TAR_OFFSET_LINKNAME], 100);
303 :
304 : /* Compute number of padding bytes. */
305 0 : mystreamer->pad_bytes_expected = tarPaddingBytesRequired(member->size);
306 :
307 : /* Forward the entire header to the next astreamer. */
308 0 : astreamer_content(mystreamer->base.bbs_next, member,
309 0 : buffer, TAR_BLOCK_SIZE,
310 : ASTREAMER_MEMBER_HEADER);
311 :
312 0 : return true;
313 0 : }
314 :
315 : /*
316 : * End-of-stream processing for a tar parser.
317 : */
318 : static void
319 0 : astreamer_tar_parser_finalize(astreamer *streamer)
320 : {
321 0 : astreamer_tar_parser *mystreamer = (astreamer_tar_parser *) streamer;
322 :
323 0 : if (mystreamer->next_context != ASTREAMER_ARCHIVE_TRAILER &&
324 0 : (mystreamer->next_context != ASTREAMER_MEMBER_HEADER ||
325 0 : mystreamer->base.bbs_buffer.len > 0))
326 0 : pg_fatal("COPY stream ended before last file was finished");
327 :
328 : /* Send the archive trailer, even if empty. */
329 0 : astreamer_content(streamer->bbs_next, NULL,
330 0 : streamer->bbs_buffer.data, streamer->bbs_buffer.len,
331 : ASTREAMER_ARCHIVE_TRAILER);
332 :
333 : /* Now finalize successor. */
334 0 : astreamer_finalize(streamer->bbs_next);
335 0 : }
336 :
337 : /*
338 : * Free memory associated with a tar parser.
339 : */
340 : static void
341 0 : astreamer_tar_parser_free(astreamer *streamer)
342 : {
343 0 : pfree(streamer->bbs_buffer.data);
344 0 : astreamer_free(streamer->bbs_next);
345 0 : }
346 :
347 : /*
348 : * Create a astreamer that can generate a tar archive.
349 : *
350 : * This is intended to be usable either for generating a brand-new tar archive
351 : * or for modifying one on the fly. The input should be a series of typed
352 : * chunks (i.e. not ASTREAMER_UNKNOWN). See also the comments for
353 : * astreamer_tar_parser_content.
354 : */
355 : astreamer *
356 0 : astreamer_tar_archiver_new(astreamer *next)
357 : {
358 0 : astreamer_tar_archiver *streamer;
359 :
360 0 : streamer = palloc0_object(astreamer_tar_archiver);
361 0 : *((const astreamer_ops **) &streamer->base.bbs_ops) =
362 : &astreamer_tar_archiver_ops;
363 0 : streamer->base.bbs_next = next;
364 :
365 0 : return &streamer->base;
366 0 : }
367 :
368 : /*
369 : * Fix up the stream of input chunks to create a valid tar file.
370 : *
371 : * If a ASTREAMER_MEMBER_HEADER chunk is of size 0, it is replaced with a
372 : * newly-constructed tar header. If it is of size TAR_BLOCK_SIZE, it is
373 : * passed through without change. Any other size is a fatal error (and
374 : * indicates a bug).
375 : *
376 : * Whenever a new ASTREAMER_MEMBER_HEADER chunk is constructed, the
377 : * corresponding ASTREAMER_MEMBER_TRAILER chunk is also constructed from
378 : * scratch. Specifically, we construct a block of zero bytes sufficient to
379 : * pad out to a block boundary, as required by the tar format. Other
380 : * ASTREAMER_MEMBER_TRAILER chunks are passed through without change.
381 : *
382 : * Any ASTREAMER_MEMBER_CONTENTS chunks are passed through without change.
383 : *
384 : * The ASTREAMER_ARCHIVE_TRAILER chunk is replaced with two
385 : * blocks of zero bytes. Not all tar programs require this, but apparently
386 : * some do. The server does not supply this trailer. If no archive trailer is
387 : * present, one will be added by astreamer_tar_parser_finalize.
388 : */
389 : static void
390 0 : astreamer_tar_archiver_content(astreamer *streamer,
391 : astreamer_member *member,
392 : const char *data, int len,
393 : astreamer_archive_context context)
394 : {
395 0 : astreamer_tar_archiver *mystreamer = (astreamer_tar_archiver *) streamer;
396 0 : char buffer[2 * TAR_BLOCK_SIZE];
397 :
398 0 : Assert(context != ASTREAMER_UNKNOWN);
399 :
400 0 : if (context == ASTREAMER_MEMBER_HEADER && len != TAR_BLOCK_SIZE)
401 : {
402 0 : Assert(len == 0);
403 :
404 : /* Replace zero-length tar header with a newly constructed one. */
405 0 : tarCreateHeader(buffer, member->pathname, NULL,
406 0 : member->size, member->mode, member->uid, member->gid,
407 0 : time(NULL));
408 0 : data = buffer;
409 0 : len = TAR_BLOCK_SIZE;
410 :
411 : /* Also make a note to replace padding, in case size changed. */
412 0 : mystreamer->rearchive_member = true;
413 0 : }
414 0 : else if (context == ASTREAMER_MEMBER_TRAILER &&
415 0 : mystreamer->rearchive_member)
416 : {
417 0 : int pad_bytes = tarPaddingBytesRequired(member->size);
418 :
419 : /* Also replace padding, if we regenerated the header. */
420 0 : memset(buffer, 0, pad_bytes);
421 0 : data = buffer;
422 0 : len = pad_bytes;
423 :
424 : /* Don't do this again unless we replace another header. */
425 0 : mystreamer->rearchive_member = false;
426 0 : }
427 0 : else if (context == ASTREAMER_ARCHIVE_TRAILER)
428 : {
429 : /* Trailer should always be two blocks of zero bytes. */
430 0 : memset(buffer, 0, 2 * TAR_BLOCK_SIZE);
431 0 : data = buffer;
432 0 : len = 2 * TAR_BLOCK_SIZE;
433 0 : }
434 :
435 0 : astreamer_content(streamer->bbs_next, member, data, len, context);
436 0 : }
437 :
438 : /*
439 : * End-of-stream processing for a tar archiver.
440 : */
441 : static void
442 0 : astreamer_tar_archiver_finalize(astreamer *streamer)
443 : {
444 0 : astreamer_finalize(streamer->bbs_next);
445 0 : }
446 :
447 : /*
448 : * Free memory associated with a tar archiver.
449 : */
450 : static void
451 0 : astreamer_tar_archiver_free(astreamer *streamer)
452 : {
453 0 : astreamer_free(streamer->bbs_next);
454 0 : pfree(streamer);
455 0 : }
456 :
457 : /*
458 : * Create a astreamer that blindly adds two blocks of NUL bytes to the
459 : * end of an incomplete tarfile that the server might send us.
460 : */
461 : astreamer *
462 0 : astreamer_tar_terminator_new(astreamer *next)
463 : {
464 0 : astreamer *streamer;
465 :
466 0 : streamer = palloc0_object(astreamer);
467 0 : *((const astreamer_ops **) &streamer->bbs_ops) =
468 : &astreamer_tar_terminator_ops;
469 0 : streamer->bbs_next = next;
470 :
471 0 : return streamer;
472 0 : }
473 :
474 : /*
475 : * Pass all the content through without change.
476 : */
477 : static void
478 0 : astreamer_tar_terminator_content(astreamer *streamer,
479 : astreamer_member *member,
480 : const char *data, int len,
481 : astreamer_archive_context context)
482 : {
483 : /* Expect unparsed input. */
484 0 : Assert(member == NULL);
485 0 : Assert(context == ASTREAMER_UNKNOWN);
486 :
487 : /* Just forward it. */
488 0 : astreamer_content(streamer->bbs_next, member, data, len, context);
489 0 : }
490 :
491 : /*
492 : * At the end, blindly add the two blocks of NUL bytes which the server fails
493 : * to supply.
494 : */
495 : static void
496 0 : astreamer_tar_terminator_finalize(astreamer *streamer)
497 : {
498 0 : char buffer[2 * TAR_BLOCK_SIZE];
499 :
500 0 : memset(buffer, 0, 2 * TAR_BLOCK_SIZE);
501 0 : astreamer_content(streamer->bbs_next, NULL, buffer,
502 : 2 * TAR_BLOCK_SIZE, ASTREAMER_UNKNOWN);
503 0 : astreamer_finalize(streamer->bbs_next);
504 0 : }
505 :
506 : /*
507 : * Free memory associated with a tar terminator.
508 : */
509 : static void
510 0 : astreamer_tar_terminator_free(astreamer *streamer)
511 : {
512 0 : astreamer_free(streamer->bbs_next);
513 0 : pfree(streamer);
514 0 : }
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